Brazing rod for depositing diamond coating metal substrate using gas or electric brazing techniques

ABSTRACT

A brazing rod is disclosed for use in depositing an abrasive metal coating on a metal substrate. The brazing rod comprises an elongate metal tube made of a metal selected from the group consisting of copper, bronze, brass, nickel, nickel alloys, iron, cobalt and steel. A brazing mixture is contained in the metal tube and comprises a particulate abrasive material selected from the group consisting of diamond particles and mixtures of diamond particles and carbide particles. The brazing mixture further contains powdered braze alloy in which one component of the braze alloy is a member selected from the group consisting of nickel, nickel alloy, silver, silver alloy, gold, gold alloy, copper, copper alloy and mixtures thereof, and in which a second component of said braze alloy is selected from the group consisting of iron, iron alloy, cobalt, cobalt alloy, tin, tin alloy, boron, silicon, chromium, chromium alloy and mixtures thereof. The diamond particles contained in the brazing mixture are coated with a material selected from the group consisting of tungsten, molybdenum, chromium, nickel, iron, cobalt, palladium, tungsten carbide, molybdenum carbide, chromium carbide and iron carbide. The carbide particles contained in the brazing mixture are selected from the group consisting of tungsten carbide, molybdenum carbide and chromium carbide.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates broadly to the application of a hard,abrasive coating to a metal substrate. In particular, the inventionrelates to means and methods for applying a coating comprising diamondsto a metal substrate using conventional gas and electric welding orbrazing techniques.

2. State of the Art

It has been known to apply a hardfacing to a metal substrate by brazinga coating containing carbide particles such as tungsten carbide to themetal substrate. Brazing rods are available commercially that can beused to braze a coating containing carbide particles to a metalsubstrate. A & B Metal Mfg. Company, Inc. of Houston Tex. and KennametalInc. of Latrobe, Pa. produce and sell tungsten carbide brazing rods. Thetungsten carbide brazing rods are used to apply a coating of abrasivematerial to drilling tools to increase their life. The drilling toolsare commonly made with a diamond cutting surface. When the diamondsurface becomes impaired, such as by loss of diamond particles, thecoating of carbide particles to the tool will increase its lifesomewhat. It would be highly advantageous and desirable if the diamondcoating could be replaced on the tool. The tool would then be capable ofits full cutting ability.

There has been no suggestion in the prior art of being able to braze acoating containing diamond particles to a metal substrate such as adrilling tool. There are various processes that are known used fordepositing a layer of braze containing diamond particles on a metalsubstrate. All such methods universally require controlled heating ofthe substrate in a vacuum furnace. There is no suggestion of brazing acoating of braze material containing diamond particles on the metalsubstrate using conventional gas or electric welding and brazingtechniques.

In U.S. Pat. No. 5,100,045 issued to Ronald C. Wiand on Mar. 31, 1992, amethod of reconditioning brazed diamond abrasive tools is disclosed. Itis recognized in that patent that it would be highly desirable to beable to recondition or repair brazed diamond abrasive tools.Unfortunately, the method taught in U.S. Pat. No. 5,100,045 the toolthat is repaired is placed in a vacuum furnace and heated to atemperature of about 1900° F. or at least about 70° F. above the liquidmelting point or flow point of the braze. The old braze becomesthermoplastic and the diamond particles reorient to present new abradingedges. If the tool has bare or bald spots on the tool, i.e., spots wherethe original diamond particles have broken away and are no longerpresent, new brazing powder and a binder are mixed to form a brazingpaste which is placed on the tool to cover the bald spots prior to theheating of the tool in the furnace. Diamond particles are placed on thepaste, and then the tool is heated in the vacuum furnace. The new andold braze becomes thermoplastic and the old and new diamonds reorient topresent abrading edges and the brazes flow together. There is nosuggestion of using a braze rod containing a braze and diamondparticles, wherein the braze is applied directly to the surface of thetool using conventional gas and electric welding and brazing techniques.

OBJECTIVES AND BRIEF DESCRIPTION OF THE INVENTION

A principal objective of the invention is to provide a novel, brazingrod for use in depositing an abrasive coating of diamond particles on ametal substrate.

A particular objective of the present invention is to provide such abrazing rod that can be used to deposit a coating of braze and diamondparticles directly to the surface of the metal substrate usingconventional gas and electric welding and brazing techniques.

The above objectives are achieved in accordance with the presentinvention by providing a novel, unique brazing rod comprising anelongate metal tube that is filled with a braze mixture having diamondparticles distributed throughout the braze mixture. The diamondparticles must be coated with a material selected from the groupconsisting of tungsten, molybdenum, chromium, nickel, iron, cobalt,palladium, tungsten carbide, molybdenum carbide and chromium carbidebefore the diamond particles are mixed with the brazing mixture andintroduced into the metal tube.

It has been found that the brazing rod of the present invention can beused in conventional gas and electric welding and brazing procedures todeposit a coating of the braze and diamond particles to the surface of ametal substrate. It has been unexpectedly found that the coated diamondswill not float in the braze material as the braze is being welded orbrazed onto the metal substrate. The coated diamonds remain dispersed inthe liquid braze material as the liquid braze material flows onto themetal substrate.

When using uncoated diamonds, the diamond particles float to the top ofthe liquid braze as the braze flows onto the metal substrate. When thediamond particles float to the surface of the liquid braze, they are notsatisfactorily secured by the braze to the metal substrate and areeasily broken away from the tool when the tool is used in an abradingprocess. The tool to which uncoated diamonds have been brazed using abrazing rod containing the uncoated diamonds is totally useless. Incontrast, the coated diamonds are distributed through the braze materialas the liquid braze flows onto the metal substrate, and the diamonds arefirmly embedded in the braze material. As the tool is used, the brazematerial tends to wear slightly away exposing working edges of thediamond particles.

The novel, brazing rod of the present invention is especially useful inrepairing damaged tools in the field. A damaged drill bit, for example,can easily and quickly be repaired at the drilling site. The repairedtool can then be immediately placed back in service. Heretofore, thedamaged drill bit had to be sent back to the manufacturer for extensiverepairs at the manufacturer's manufacturing facilities. Unless a second,replacement drill bit was available, drilling work in the field wouldhave to stop until the repaired drill bit or a new drill bit wasreceived from the manufacturer. By using the novel, brazing rods of thepresent invention, the damaged drill bit can be repaired immediately andput back in immediate service. It should also be recognized that thenovel, brazing rods of the present invention can be used to manufacturenew tools if so desired.

Additional objects and features of the invention will become apparentfrom the following detailed description, taken together with theaccompanying drawings.

THE DRAWINGS

Preferred embodiments of the present invention representing the bestmode presently contemplated of carrying out the invention areillustrated in the accompanying drawings in which:

FIG. 1 is a cross-sectional representation of a brazing rod inaccordance with the present invention; and

FIG. 2 is a schematic, cross-sectional, representation of the brazingrod of FIG. 1 being used to deposit a braze coating containing diamondparticles to a substrate metal.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

A brazing rod 10 for use in depositing an abrasive metal coating on ametal substrate in accordance with the present invention is shown inFIG. 1 of the drawings. The metal coating that is to be deposited by useof the brazing rod 10 contains an abrasive material selected from thegroup consisting of diamond particles and mixtures of diamond particlesand carbide particles.

As shown, the brazing rod comprises an elongate metal tube 12 made of ametal selected from the group consisting of copper, bronze, brass,nickel, nickel alloys, iron, cobalt and steel. A brazing mixture 16 iscontained in the metal tube 12. The brazing mixture comprises a powderedbraze alloy in which a particulate abrasive material is disposed. Theparticulate abrasive material is selected from the group consisting ofdiamond particles and mixtures of diamond particles and carbideparticles.

It is essential that the diamond particles be coated with a materialselected from the group consisting of tungsten, molybdenum, chromium,nickel, iron, cobalt, palladium, tungsten carbide, molybdenum carbideand chromium carbide. The carbide particles are selected from the groupconsisting of tungsten carbide, molybdenum carbide, chromium carbide andiron carbide.

The powdered braze alloy comprises at least two components. Onecomponent of the braze alloy is a member selected from the groupconsisting of nickel, nickel alloy, silver, silver alloy, gold, goldalloy, copper, copper alloy and mixtures thereof. The second componentof the braze alloy is selected from the group consisting of iron, ironalloy, cobalt, cobalt alloy, tin, tin alloy, boron, silicon, chromium,chromium alloy and mixtures thereof.

In a preferred embodiment of the brazing rod 10 of the presentinvention, the brazing mixture contained in the metal tube 12 furthercomprises a finely divided, particulate material selected from the groupconsisting of tin, silver, brass, lead, cadmium, indium and mixturesthereof. The diamond particles are preferably coated with a materialselected from the group consisting of tungsten, molybdenum, chromium,tungsten carbide, molybdenum carbide and chromium carbide. In accordancewith a particularly preferred embodiment of the invention, theparticulate abrasive material consists essentially of diamond particleswhich have been coated as specified above.

The brazing rod 10 of the present invention is produced by first coatingdiamond particles with a material selected from the group consisting oftungsten, molybdenum, chromium, nickel, iron, cobalt, palladium,tungsten carbide, molybdenum carbide, chromium carbide and siliconcarbide. The coated, diamond particles are then mixed with a powderedbraze alloy to form a braze mixture 16.

The braze alloy has at least two components. One component is a memberselected from the group consisting of nickel, nickel alloy, silver,silver alloy, gold, gold alloy, copper, copper alloy and mixturesthereof. The second component of the braze alloy is selected from thegroup consisting of iron, iron alloy, cobalt, cobalt alloy, tin, tinalloy, chromium, chromium alloy and mixtures thereof. The braze mixture16 is then introduced into the core of an elongate, metal tube 12 thatis made of a metal selected from the group consisting of copper, bronze,brass, nickel, nickel alloys, iron, cobalt and steel.

In a preferred embodiment of the present invention, finely divided,particulate material selected from the group consisting of tin, silver,brass, lead, cadmium, indium and mixtures thereof is mixed with thecoated diamond particles and powdered brazing alloy in making the brazemixture 16 that is introduced into the metal tube 12. Supplementalabrasive particles can be added to the braze mixture 16 together withthe diamond particles if so desired. The supplemental abrasive particlesare selected from the group consisting of tungsten carbide, molybdenumcarbide, and chromium carbide.

It has been unexpectedly found that the brazing rods 10 of the presentinvention can be used with conventional gas or electric brazing andwelding techniques to apply a braze coating containing diamonds to ametal substrate. As shown in FIG. 2, the braze rod 10 can be used with agas flame. The flame 20 is directed to the distal end of the rod 10 andonto the metal substrate.

The flame 20 heats the metal substrate 22 and melts the tip of the metaltube 12 of the rod 10. The powdered bronze alloy contained in the brazemixture 16 in the metal tube 12 melts with the melting of the tip of themetal tube 12. The melted braze mixture 16 and the metal of the metaltube 12 flow onto and wet the surface of the metal substrate 22.

The coated diamond particles 24 (FIG. 2) flow with the liquified brazematerial 16, and when the braze material 16 solidifies on the metalsubstrate 22, the coated diamond particles 24 are unexpected found to besubstantially uniformly distributed through the braze coating. Ifuncoated diamonds are employed in the braze mixture 16 of the braze rod10, instead of coated diamonds in accordance with the present invention,the uncoated diamonds float to the exposed surface of the braze coatingbefore the braze material solidifies and are not adequately bonded tothe braze coating and thus the metal substrate 22.

The brazing rods 10 of the present invention are highly desirable forbeing used in repairing and reconditioning diamond faced tools. Thetools, such as drilling bits, can be repaired and reconditioned in thefield. For example, a drilling bit can be repaired by brazing a coatingof diamonds on the worn or damaged bit to replace the diamonds that havebeen lost from the surface of the bit by wear or other damage to thebit. Using the brazing rods 10 of the present invention, a braze coatingof diamonds is quickly and inexpensively brazed on the damaged or wornsurfaces of the drill bit in the field. The drill bit need not beshipped to a repair facility but instead can be repaired quickly in thefield and then returned immediately to service.

The invention will be further illustrated by the following examples:

EXAMPLE 1

Diamond particles can be coated by any of numerous methods known in theart. U.S. Pat. Nos. 3,371,840 and 4,770,907 disclose methods of coatingdiamond grit with various coatings applicable in the present invention.In this example, diamond particles were coated by placing the diamondgrit in a stainless steel crucible together with a salt mixtureconsisting of equal parts sodium chloride, potassium chloride andcalcium chloride. Powdered chromium metal in an amount of about 0.5%based on the salt mixture, was added to the crucible along with thediamond grit in which the diamond particles had a size of -30+40 mesh.The crucible containing the salt mixture, chromium metal and diamondgrit was heated in a furnace to a temperature of 1000° C. for 2 hours tocoat the diamond particles with a coating consisting of chromiumcarbide.

A braze mixture was made by mixing 1 gram of the chromium carbide coateddiamonds with 2 grams of a commercially available braze powder (LM brazepowder from Wall Colmonoy Corporation). The braze mixture also had 1gram silver flake, 2 grams bronze powder, 1 gram tin powder and 1 gramflux mixed therewith.

The braze mixture was then introduced into the core of a copper tube tomake a braze rod. The copper tube was 12 inches in length and had aninternal diameter of 5/32 inch. The core of the copper tube was filledsubstantially uniformly throughout the length of the tube.

The braze rod consisting of the copper tube containing the braze mixturewas used to braze a braze coating on a steel substrate. The copper tubebraze rod was relatively easy to use. The braze coating had coateddiamond particles distributed substantially uniformly through the brazecoating. The coated diamonds did not float or migrate to the exposedsurface of the braze coating, and unlimited layers of the braze coatingcould be layered down without the diamonds floating and disbonding fromthe deposit.

EXAMPLE 2

The procedure of Example 1 was followed with the sole exception that thebraze mixture was introduced into the core of a brass tube to make abraze rod. The brass tube was 12 inches in length and had an internaldiameter of 5/32 inch. The core of the brass tube was filledsubstantially uniformly with the braze mixture.

The braze rod consisting of the brass tube containing the braze mixturewas used to braze a braze coating on a steel substrate. The brazecoating had coated diamond particles distributed substantially uniformlythrough the coating. The coated diamonds did not float or migrate to theexposed surface of the braze coating. The brass tube brazing rod was notquite as easy to use as the copper tube brazing rod.

EXAMPLE 3

The procedure of Example 1 was followed with the sole exception that thebraze mixture was introduced into the core of a stainless steel tube tomake a braze rod. The steel tube was 12 inches in length and had aninternal diameter of 5/32 inch. The core of the steel tube was filledsubstantially uniformly with the braze mixture.

The braze rod consisting of the steel tube containing the braze mixturewas used to braze a braze coating on a steel substrate. The brazecoating had coated diamond particles distributed substantially uniformlythrough the coating. The coated diamonds did not float or migrate to theexposed surface of the braze coating.

The steel tube brazing rod was more difficult to use than either thebrazing rods made from copper or brass tubes. The reason was that thesteel had a melting temperature that was somewhat higher than themelting temperature of the braze material contained in the steel rod. Askilled welder was however able to use the brazing rod made from thestainless steel tube. The skilled welder thought that the use of thestainless steel tube would have been easier if very thin walled tubinghad been employed in making the brazing rod.

EXAMPLE 5

A copper brazing rod produced in accordance with the procedure given inExample 1 was used to apply a braze coating to the end of a piece ofsteel pipe. The pipe had an exterior diameter of 3/4 inch. The end ofthe pipe was uniformly coated with a braze, and the diamond particles inthe braze were substantially uniformly distributed through the brazecoating.

The pipe was secured in the chuck of a drill press so that the coatedend of the pipe could be forced into contact with an item to be drilled.The pipe was used to drill holes through various types of rocks. A smallamount of water coolant was sprayed on the rocks as they were beingdrilled.

The pipe successfully drilled through a piece of obsidian rock that wastwo inches in thickness and a piece of agate rock that was one inch inthickness. The pipe was used to drill holes in numerous additional rocksof less hardness than obsidian and agate. After numerous drillings, theend of the pipe still had its braze coat intact and in its originalcondition. The pipe was capable of many additional drillings.

Although a preferred embodiment of a braze rod of the present inventionhas been illustrated and described, it is to be understood that thepresent disclosure is made by way of example and that various otherembodiments are possible without departing from the subject mattercoming within the scope of the following claims, which subject matter isregarded as the invention.

I claim:
 1. A brazing rod for use in depositing an abrasive metalcoating on a metal substrate, wherein the metal coating contains anabrasive material selected from the group consisting of diamondparticles and mixtures of diamond particles and carbide particles, saidbrazing rod comprisingan elongate metal tube made of a metal selectedfrom the group consisting of copper, bronze, brass, nickel, nickelalloys, iron, cobalt and steel; and a brazing mixture contained in saidmetal tube, said brazing mixture comprising a particulate abrasivematerial selected from the group consisting of diamond particles andmixtures of diamond particles and carbide particles; and powdered brazealloy in which one component of the braze alloy is a member selectedfrom the group consisting of nickel, nickel alloy, silver, silver alloy,gold, gold alloy, copper, copper alloy and mixtures thereof, and inwhich a second component of said braze alloy is selected from the groupconsisting of iron, iron alloy, cobalt, cobalt alloy, tin, tin alloy,boron, silicon, chromium, chromium alloy and mixtures thereof, wherein(a) the diamond particles have been coated with a material selected fromthe group consisting of tungsten, molybdenum, chromium, nickel, iron,cobalt, palladium, tungsten carbide, molybdenum carbide, chromiumcarbide and iron carbide, and (b) the carbide particles are selectedfrom the group consisting of tungsten carbide, molybdenum carbide andchromium carbide.
 2. A brazing rod in accordance with claim 1 whereinsaid brazing mixture contained in said metal tube further comprises afinely divided, particulate material selected from the group consistingof tin, silver, brass, lead, cadmium, indium and mixtures thereof.
 3. Abrazing rod in accordance with claim 2 wherein the diamond particleshave been coated with a material selected from the group consisting oftungsten, molybdenum, chromium, titanium, niobium, zirconium, tungstencarbide, molybdenum carbide, chromium carbide, titanium carbide, niobiumcarbide and zirconium carbide.
 4. A brazing rod in accordance with claim3 wherein said brazing mixture contained in said metal tube furthercomprises a finely divided, particulate material selected from the groupconsisting of tin, silver, brass, lead, cadmium, indium and mixturesthereof.
 5. A brazing rod in accordance with claim 4 wherein theparticulate abrasive material consists essentially of diamond particles.6. A method of making a brazing rod for use in depositing a metalcoating on a metal substrate, wherein the metal coating contains diamondparticles, said method comprising(a) coating diamond particles with amaterial selected from the group consisting of tungsten, molybdenum,chromium, nickel, iron, cobalt, palladium, tungsten carbide, molybdenumcarbide and chromium carbide; (b) mixing the coated, diamond particlesfrom step (a) with a powdered braze alloy in which one component of thebraze alloy is a member selected from the group consisting of nickel,nickel alloy, silver, silver alloy, gold, gold alloy, copper, copperalloy and mixtures thereof, and in which a second component of saidbraze alloy is selected from the group consisting of iron, iron alloy,cobalt, cobalt alloy, tin, tin alloy, boron, silicon, chromium, chromiumalloy and mixtures thereof; and (c) filling the core of an elongate,metal tube with the mixture from step (b), wherein said metal tube ismade of a metal selected from the group consisting of copper, bronze,brass, nickel, nickel alloys, iron, cobalt and steel.
 7. A method ofmaking a brazing rod in accordance with claim 6 wherein a finelydivided, particulate material selected from the group consisting of tin,silver, brass, lead, cadmium, indium and mixtures thereof is mixed withthe coated diamond particles and powdered brazing alloy in step (b). 8.A method of making a brazing rod in accordance with claim 6 whereinabrasive particles selected from the group consisting of tungstencarbide, molybdenum carbide and chromium carbide are mixed with thecoated diamond particles and powdered brazing alloy in step (b).